Method and apparatus for low temperature pyrometry useful for thermally processing silicon wafers

A thermal processing system, comprising:

• a controllable radiant heat source for heating a substrate disposable on a front side thereof;
• at least one transmission pyrometer disposed on a side of said substrate opposite said radiant heat source;
• and
• a power supply control system controlling an amount of power delivered to said radiant heat source and including
• a memory stored with unnormalized characteristics relating photocurrents produced by said transmission pyrometer for multiple values of a temperature of said substrate and multiple values of a variable representative of a temperature of a filament of a lamp in said radiant heat source,
• means for measuring a normalizing photocurrent from said transmission pyrometer for a set temperature of said filament and a known temperature of said substrate;
• and
• means for normalizing said stored unnormalized characteristics according to said measured normalizing photocurrent.

A thermal processing system, comprising:

• a radiant heat source including incandescent lamps;
• a support for supporting a wafer in opposition to said radiant heat source;
• a reflector plate disposed on a side of said support opposite said radiant heat source;
• a light pipe having an input end optically coupled through an aperture in said reflector plate, supported by the reflector plate, and directed at said wafer;
• an optical beam splitter receiving an output of said light pipe and dividing said output into first and second beams;
• a transmission pyrometer receiving said first beam;
• and
• a radiation pyrometer receiving said second beam.

A dual pyrometer, comprising:

• a beam splitter receiving a signal from a light guide and dividing it into a first beam reflected from a reflective face and a second beam not reflected from the reflective face;
• a transmission pyrometer receiving said first beam;
• and
• a radiation pyrometer receiving said second beam.

A dual pyrometer, comprising:

• a beam splitter receiving a signal from a light guide and dividing it into a first beam and a second beam;
• a transmission pyrometer receiving said first beam;
• and
• a radiation pyrometer receiving said second beam,
• wherein said transmission and radiation pyrometers are configured to detect a temperature of a silicon wafer.